Controlled tool for machining compound surfaces

ABSTRACT

A machine tool with a wheel for precision grinding of a ball end mill with cylindrically surfaced lands and a hemispherical end includes a template conforming to the lands and ball end mounted on a hydraulic driven workpiece table on which the ball end mill is held in a rotatable chuck. The grinding wheel is mounted on another hydraulically driven table, relative movement of the tables being hydraulically controlled by a stylus which senses the template. During grinding the ball end mill is supported and rotated by a finger mounted on the grinding wheel table which engages in the flutes between the lands of the ball end mill closely adjacent the wheel. The wheel grinds along the lands and then as grinding continues around the ball end a sliding block supporting the finger engages a stop on the workpiece table and retracts the finger from the path of the wheel around the ball end. To maintain the same spacial relation between the wearing edge of the wheel and the ball end mill as the stylus has with the workpiece template, the wheel is dressed with a truing tool on the workpiece table under the control of a dressing template. The grinding wheel is first advanced toward the truing tool by a stepping motor independently of the hydraulic table drive so that when the wearing edge is trued, the original spacial relationship of wearing edge and ball end mill is restored.

United States Patent 91 Williams et al.

[ Jan.30,1973

154] CONTROLLED TOOL FOR MACHINING COMPOUND SURFACES [75] Inventors:Thurston V. Williams, Wilton; Leo H. Cheever, South Lyndeboro, both ofNH.

[73] Assignee: The O. K. Tool Company, Inc.

[22] Filed: May 14,1971

[21] Appl. No.: 143,557

Primary Examiner-Donald G. Kelly Attorney-James H. Grover [57] ABSTRACTA machine tool with a wheel for precision grinding of a ball end millwith cylindrically surfaced lands and a hemispherical end includes atemplate conforming to the lands and ball end mounted on a hydraulicdriven workpiece table on which the ball end mill is held in a rotatablechuck. The grinding wheel is mounted on another hydraulically driventable, relative movement of the tables being hydraulically controlled bya stylus which senses the template. During grinding the ball end mill issupported and rotated by a finger mounted on the grinding wheel tablewhich engages in the flutes between the lands of the ball end millclosely adjacent the wheel. The wheel grinds along the lands and then asgrinding continues around the ball end a sliding block supporting thefinger engages a stop on the workpiece table and retracts the fingerfrom the path of the wheel around the ball end. To maintain the samespacial relation between the wearing edge of the wheel and the ball endmill as the stylus has with the workpiece template, the wheel is dressedwith a truing tool on the workpiece table under the control of adressing template. The grinding wheel is first advanced toward thetruing tool by a stepping motor independently of the hydraulic tabledrive so that when the wearing edge is trued, the original spacialrelationship of wearing edge and ball end mill is restored.

6 Claims, 9 Drawing Figures PATENTED M30 I973 SHEET 1 [IF 2 &

FIG. I

PAIENIEDJAR30 I975 3, 713 5 SHEET 2 0F 2 INVENTORS THURSTON v. WILLIAMSLEO H. CHEEVER ATTORNEY CONTROLLED TOOL FOR MACHINING COMPOUND SURFACESReference is made to U.S. Pat. No. 3,538,649 granted Nov. 10, 1970 toThurston V. Williams.

BACKGROUND OF THE INVENTION Various machined workpieces have compoundsurfaces which, after rough forming, require precision grinding, millingor like machining to close tolerances in the order of one or a few tenthousandths of an inch along a straight longitudinal surface of theworkpiece and then along an adjacent surface which curves or angles awayfrom the straight surface. Example of such workpieces are multiplediameter counterbores and ball end mills. A ball end mill haslongitudinal lands and intermediate flutes terminating in ahemispherical or otherwise curved ball end whose curve may be tangent toor continuous with the generally cylindrical surface of the lands. Inthe usual method of grinding a ball end mill the ball end mill is heldrotatably in a collet chuck and the land being ground is supported by afinger closely adjacent the grinding edge or wearing surface of thegrinding wheel. The finger engages in a flute under the land keeping theland being ground in correct position and preventing deflection of theball end mill. Hitherto, when grinding of the land was completedgrinding could not be continued transversely of the land around the ballend because of the interposition of the finger between the grinding edgeand the ball end, and the grinding machine had to be stopped and themachine manually readjusted, so that further grinding left anundesirable discontinuity between the land and ball end as well asexpending time in stopping, readjusting and restarting grinding.

Thus one object of the present invention is to provide a way in whichlongitudinal and transverse portions of a workpiece such as the land andball end may be supported by a finger and ground or otherwise machinedin one continuous pass.

A further object is to make possible the continuous precision grindingof longitudinal and transverse portions of a workpiece under the controlof a template and a follower for sensing the template.

A still further object is to maintain a precise predeterminedrelationship between the sensing follower and the wearing surface of thegrinding wheel or similar work tool.

SUMMARY OF THE INVENTION According to the invention apparatus forcontinuous machining of adjacent longitudinal and transverse portions ofa workpiece comprises a work tool table holding a work tool, a workpiecetable holding said workpiece, control means for said tables for causingrelative machining movement of the work tool on a path along theportions of the workpiece, a finger yieldingly mounted on the work tooltable for moving engagement of the workpiece and means on the workpiecetable positioned to move the finger relative to the workpiece out of thepath of the work tool as the template guides movement of the work toolon the transverse portion of the workpiece, whereby said relativemachining movement proceeds between the longitudinal and the transverseportions of the workpiece uninterrupted by adjustment of the work toolor workpiece holder relative to their respective tables.

Further according to the invention the aforesaid control means comprisesa guide template on the workpiece table conforming to the adjacentportions of the workpiece, a follower on the work tool table, forsensing the template, drive means for said tables responsive to thefollowers sensing of the template for causing relative machiningmovement of the work tool on a path along the adjacent portions of theworkpiece.

Still further according to the invention the aforesaid work tool has awearing surface and the apparatus comprises a dressing tool on saidworkpiece table for truing said wearing surface when worn, a dressingtemplate on the workpiece table disposed in the same spatial relation tothe dressing tool as the first said template has to the workpiece,means, independent of the drive means, for advancing the work tooltoward said dressing tool while maintaining said spatial relationbetween the dressing tool and dressing template, whereby said drivemeans, in response to the followers sensing of the dressing templatecauses said dressing tool to dress said wearing surface to the aforesaidspatial relation.

DRAWINGS For the purpose of illustration typical embodiments of theinvention are shown in the accompanying drawings in which:

FIG. 1 is a plan view of a template controlled machine tool with a wheelfor grinding a ball end mill, part being broken away;

FIG. 2 is a fragmentary plan view like FIG. 1 showing the broken awaypart;

FIG. 3 is an elevation of a ball end mill;

FIG. 4 is a side elevation, enlarged, of the grinding wheel and ball endmill of FIG. 1;

FIG. 5 is a front elevation, enlarged, of the grinding wheel andadjacent parts of FIG. 1; and

FIGS. 6 to 9 are plan views of details of FIG. 1.

DESCRIPTION workpiece, Work Tool and workpiece Template Shown in FIGS. 1and 2 is a machine tool set up for grinding a ball end mill 1 workpieceshown in detail in FIGS. 3 and 4. The ball end mill has a shank 2 andtwo spiral lands 3 on a straight cylindrical surface and flutes 4extending to a rounded end 6. The cutting edges of the end mill extendlongitudinally along the lands a constant distance from the center lineof the end mill, and then generally transversely around the ball. Thework tool for sharpening this cutting edge is a cupshaped abrasivegrinding wheel 7 having a grinding surface 8 which wears where its outeredge 9 grinds the land 3 (see FIG. 4). As will be described in greaterdetail the ball end mill is ground under the control of a stylus orfollower 11 which senses a template 12 having a lead in portion 13, astraight portion 14, and a quarter circular portion 16. The straight andcircular portions of the template conform precisely (within 1 mil orbetter) to the desired ground contour of the straight cylindricalportion of the lands and the ball end respectively.

Machine Tool As a Whole Referring to FIG. 1, the machine tool as a wholecomprises a base 21 on which are slidingly mounted a workpiece table 22and a work tool table 23. The tables 22 and 23 may be reciprocated inthe directions of the arrows 22' and 23' respectively by the usualmanual adjustments (not shown) or by hydraulic pistons 24 and 26. Fluidis applied to the cylinders through conduits 25 from a hydraulic controlgenerator 27 under the control of an operator control 28 and a valvingor tracer box 29 operated by the template sensing stylus or follower 11.The template controlled hydraulic system is known available under thetrademark TRUETRACE from True Trace Corp., Covina, Calif.

Attached to the workpiece table is a free rotating collet chuck 31gripping the shank 2 of the ball end mill 1 to a repeatable'depthandallowing the end mill to rotate. The workpiece template 12 is alsomounted on an extension 32 of the workpiece table 22 by means of a clamp33 which is micrometrically adjustable by thumb screws 34 and 36. In thepreliminary setting up of the machine tool for precisely identicalgrinding of a number of ball end mills, the workpiece template 12 isadjusted to the same spatial relation with respect to the collet chuck31 and the end mill 1 held therein as the template follower 11 bears tothe wearing surface of the grinding wheel 7.

The grinding wheel 7 is carried on the shaft of a spindle 45 driven byan electric motor 47 attached to an auxiliary table 48. The auxiliarytable 48 in turn is slidingly mounted on a base 44 attached to the worktool table 23. A stepping motor 49 is coupled to a worm 50 by a pulley51. When the motor 49 is stepped one or more fractions of a revolutionby closing a key 52 or like switching means in the operator control 28,the worm, which is journalled in a bracket 53 on the base 44, advancesthe auxiliary table 48 in the direction of the broken arrow 48' for apurpose to be explained in the section entitled Work Tool Dressing. Ashas been mentioned the work tool table 23 together with the auxiliarytable 48 and grinding work tool 7 is reciprocated in the direction ofarrow 23.

In general operation of the machine tool, grinding of each ball end millis initiated by using the operator control to supply the workpiece tablehydraulic cylinder 24 and the work tool table hydraulic cylinder 26simultaneously moving the workpiece table 22 to the left and the worktool table 23 toward the bottom from the positions shown in FIG. 1. Thismovement continues until the template follower 11 on the work tool tabletouches the lead in portion 13 of the template 12 on the workpiecetable. After the follower senses the template the automatic hydraulicsystem precisely moves the tables so that the follower traces down thelead in portion 13 to the straight portion 14 of the template (FIG. 6).Simultaneously the wearing edge of the grinding wheel 7 approaches andbegins grinding one land 3 of the ball end mill as the workpiece table22 is now moved to the right.

Workpiece Support Finger The template controlled guiding of the grindwheel 7 relative to the ball end mill workpiece 1 can machine theworkpiece to within one thousandth of an inch and even greater accuracy.However, to hold such accuracy it is necessary to support the workpieceagainst flexing. Also in the case of a ball end mill with spiral landsthe end mill must be rotated on its centerline as the grinding wheelpasses along the land to present the portion of the land being ground tothe wheel. For this purpose it is known to mount on the work tool table23 a metal finger 60 having a tip 61 engaging a flat portion of the endmill flute 4 under the land 3 being ground (FIG. 4).

The finger is positioned very close, within a fraction of an inch, tothe grinding wheel, and extends beyond the wheel as shown in FIG. 6. Asthe workpiece table 'moves to the left the finger 60 resists deflectionof the end mill by the grinding force, and by sliding along the flutecauses the end mill to rotate along with its free rotating chuck 31.

When however, the finger reaches the ball end its close proximity to thewheel interposes the tip between the wheel and the ball end. Hitherto ithas been necessary to interrupt grinding at the end of the straight passalong the land and rotate the collet chuck 31 on a vertical axis duringgrinding around the ball end or other transverse portion of a workpiece.Consequently the original predetermined relation between the tracingtemplate and the workpiece is disrupted preventing use of the templateto control the ball end grinding and requiring time consuming andlaborious manual resetting of the relation between the template 12 andworkpiece. Moreover, the interruption of template control results informing a discontinuity between the ground surface of the land and ofthe ball end. The ball end mill and whatever bore it is intended to millwill therefore have an angle or burr instead of a smooth blend desiredbetween their straight and curved portions.

According to the present invention it is possible to blend the straightand curved portions and make one continuous template controlled grind byyieldingly mounting the finger 60.

As shown in FIGS. 1, 5, 6 and 7 the finger mount comprises a rectangularbase block 62 supported on a rod 63 fixed to a clamp 64 on the auxiliarytable 48 carried on the work tool table 23. Dovetailed into the block 62is a slide 66. Springs 67 compressed between an upstanding back wall 68and the slide yieldingly urge the slide away from the back wall to thedistance shown in FIG. 6 limited by the head of a cap screw 69 set inthe slide. A post 71 upstanding from the slide 66 has the finger 60secured at its upper end. Thus the slide and finger are arranged to moverelative to the grinding wheel 7 between the positions shown in FIGS. 6and 7.

Whereas the grinding wheel 7 and the finger base block 62 are fixedrelative to the auxiliary table 48 on the work tool table 23, a screwstop 72 is fixed relative to the workpiece table 22. The stop is mountedin a bracket 73 slidably adjustably in a slotted block 74 on theworkpiece table so that the stop may be set opposite the dovetail slide66. The stop is adjustable toward and away from the slide.

When during the grinding of the ball end mill- 1 the grinding proceedsfrom the straight pass along the land 3 to the circularly transverseball end portion 6, the stop engages the dovetail slide 66 as shown inFIG. 7,

. and relatively moves the slide and finger 60 rearwardly and inwardlyof the grinding wheel 7. Actually the forward progress of the work toolcontinues while movement of the finger and slide is arrested by thestop. But, relative to the wheel 7 the finger moves out of the way ofthe grinding edges as the grinding edge passes half way around the ballend, while remaining in supporting engagement under the land beingground.

The land can thus be ground along its straight portion 3 and ball end 6continuously and under the precise control of the straight and curvedportions 14 and 16 of the workpiece template 12. The two portiongrinding pass can be completed quickly without disrupting the originalset up of the relation between the workpiece template l2 and thepredetermined workpiece position in the collet chuck, and the samerelation between the template follower 11 and the grinding edge of thewheel 7. Successive ball end mills can be repeatedly gripped in the sameposition in the chuck and a large number of end mills precisely groundto the same tolerance.

Dressing of Work Tool While the grinding edge 8 of the wheel 7 holds itsshape and its predetermined relation to the template follower stylus 11for many passes it will ultimately wear or be chipped and, as shown inFIGS. 8 and 9, require dressing or truing. Further according to thepresent invention the wheel may be dressed and trued without destroyingits aforesaid predetermined relation with the follower 11.

As shown in FIGS. 1 and 2 the machine tool is provided with a swingingbracket 80 having an arm 81 pivotted on a pin 82 supported on theextension 32 of the workpiece table. The bracket 80 carries a diamondpoint dressing tool 83 and a dressing template 84 in a predeterminedstationary relationship, although the dressing template may bemicrometrically adjusted like the workpiece template 12 in the initialset up of the machine tool.

For a dressing operation the collet chuck 31 and workpiece table aremoved away from the wheel 7. The dressing bracket 80 is then swung downclose to the position shown in FIG. 2 and the sliding block 62 andsupport finger 60 removed. The diamond point dressing tool 83 is thenopposite the grinding wheel 7 and the dressing template near the stylusfollower 11. The auxiliary table 48 is then stepped a few increments inthe direction of the broken arrow 48' by closing the operator control 52for the stepping motor 49 and worm 50. The amount of advance is slightlymore than the amount of wear of the cutting edge 8 of the wheel 7. Thestepped advance of the auxiliary table is independent of thehydraulically controlled movements of the work tool table andtemporarily changes the relation between the follower l 1 and the wheel7.

The hydraulic system is then activated moving the work tool andworkpiece tables so that the follower 11 is led into the dressingtemplate 84 similiarly as with the workpiece template 14. Underhydraulic template control the stylus progresses along the template tothe transverse portion (FIGS. 8 and 9). Simultaneously the diamond point83 moves in and begins truing the face of the grinding wheel (FIG. 9).When the dressing pass is completed the wearing edge 8 will be trued tothe original shape shown in FIGS. 5 to 7, and the predetermined relationbetween the stylus follower 11 and the wearing edges will be restored toequivalence with the relation between the workpiece l and workpiecetemplate 12. The dressing bracket 84 may then be swung out of the wayand grinding of ball end mill workpieces may be resumed without changingthe original machine set up and with assurance that after dressingworkpieces will be ground to the same precise dimensions as beforedressing.

It should be understood that the present disclosure IS for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

We claim:

1. Apparatus for continuous machining of adjacent longitudinal andtransverse portions of a workpiece, comprising:

a work tool table holding a work tool,

a workpiece table holding said workpiece,

control means for said tables for causing relative machining movement ofthe work too] on a path along the portions of the workpiece,

a workpiece support yieldingly mounted on the work tool table for movingengagement of the workpiece and actuating means on the workpiece tablepositioned to move the support relative to the workpiece out of the pathof the work tool as the control means causes movement of .the work toolon the transverse portion of the workpiece,

whereby said relative machining movement proceeds between thelongitudinal and the transverse portions of the workpiece uninterruptedby adjustment of the work tool or workpiece holder relative to theirrespective tables.

2. Apparatus according to claim 1 wherein said workpiece supportcomprises a finger engaging the workpiece in opposition to the workingforce of the work too], said finger being mounted to move laterally ofthe direction of the working force.

3. Apparatus according to claim 2 wherein said finger is mounted on asliding carrier.

4. Apparatus according to claim 3 wherein the aforesaid actuating meanscomprises a stop located in the path of the sliding carrier duringmachining movement on transverse portions of the workpiece.

5. Apparatus according to claim 4 wherein said finger is disposed inclose proximity to the working surface of said work tool, and said stopand carrier are spaced away from the work tool.

6. Apparatus according to claim 1, wherein said con trol meanscomprises:

a guide template on the workpiece table conforming to said adjacentportions of the workpiece,

a follower on the work tool table, for sensing the template,

drive means for said tables responsiveto the followers sensing of thetemplate for causing relative machining movement of the work tool on apath along the adjacent portions of the workpiece.

1. Apparatus for continuous machining of adjacent longitudinal andtransverse portions of a workpiece, comprising: a work tool tableholding a work tool, a workpiece table holding said workpiece, controlmeans for said tables for causing relative machining movement of thework tool on a path along the portions of the workpiece, a workpiecesupport yieldingly mounted on the work tool table for moving engagementof the workpiece and actuating means on the workpiece table positionedto move the support relative to the workpiece out of the path of thework tool as the control means causes movement of the work tool on thetransverse portion of the workpiece, whereby said relative machiningmovement proceeds between the longitudinal and the transverse portionsof the workpiece uninterrupted by adjustment of the work tool orworkpiece holder relative to their respective tables.
 1. Apparatus forcontinuous machining of adjacent longitudinal and transverse portions ofa workpiece, comprising: a work tool table holding a work tool, aworkpiece table holding said workpiece, control means for said tablesfor causing relative machining movement of the work tool on a path alongthe portions of the workpiece, a workpiece support yieldingly mounted onthe work tool table for moving engagement of the workpiece and actuatingmeans on the workpiece table positioned to move the support relative tothe workpiece out of the path of the work tool as the control meanscauses movement of the work tool on the transverse portion of theworkpiece, whereby said relative machining movement proceeds between thelongitudinal and the transverse portions of the workpiece uninterruptedby adjustment of the work tool or workpiece holder relative to theirrespective tables.
 2. Apparatus according to claim 1 wherein saidworkpiece support comprises a finger engaging the workpiece inopposition to the working force of the work tool, said finger beingmounted to move laterally of the direction of the working force. 3.Apparatus according to claim 2 wherein said finger is mounted on asliding carrier.
 4. Apparatus according to claim 3 wherein the aforesaidactuAting means comprises a stop located in the path of the slidingcarrier during machining movement on transverse portions of theworkpiece.
 5. Apparatus according to claim 4 wherein said finger isdisposed in close proximity to the working surface of said work tool,and said stop and carrier are spaced away from the work tool.